Process of isolating quercitrin



Patented Dec. It), 1950 PROCESS OF ISOLATING QUERCITRIN Floyd De Eds, San Francisco, and Albert N. Booth, Berkeley, Calif., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application October 14, 1949, Serial No. 121,442

Claims. (Cl. 260-210) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, if patented in any country may be manufactured and used by or for the Government of the United us of any royalty thereon.

materials.

action as does rutin.

also useful as dyestuffs.

dyestuffs.

extract. the trade as quercitron or fiavine.

tains the quercitrin.

some techniques.

Organischen Chemie, 4th

With boiling 85% with hydrogen sulphide, evaporation of the purified filtrate to dryness and extraction ofv the residue with alcohol, precipitation of the quercitrin from the alcohol solution, and finally 4 This process The alcohol phase whereas the The extraction is generally con- Further, in

In this extraction concentra- 5 or 5 recrystallizations from water. States Of America for governmental purposes possesses the disadvantage that it involves a throughout the world without the payment to multip y of Operations which renders it unfeasable for commercial operation.

This invention relates to the isolation of We have now found that quercitrin may be quercitrin and quercetin from black oak bark lated by a relatively Simple and ecchomical extract or other quercitrin-containing source process wherein high yields (practically quantitative) of quercitrin are obtained in pure form.

Quercitrin is useful for therapeutic purposes The process of this invention essentially involves as it possesses the same type of physiological two distinct steps, as follows:

Since quercitrin is the In the first step, the quercitrin source material rhamnoside of quercetin it may be used for the is extracted with an aqueous alcohol, the conpreparation of quercetin by subjecting it to centration of alcohol with respect to water being hydrolysis to split off the rhamnose portion of from about 5% to about 50%, by volume. the molecule. Both quercitrin and quercetin are extract so obtained is discarded and the insol- 29 uble solid residue is retained. In this step, the

In accordance with this invention, quercitrin gross impurities such as tannins are removed is isolated from. materials containing the same, from the source material since they are soluble particularly from black oak bark. Particularly in the aqueous useful raw materials are the powdered black oak quercitrin is relatively insoluble in this phase. bark extracts sold in the open market as yellow Although we prefer to use ethanol as the alcohol These solid products are generally in this extraction procedure, other water-miscible prepared from black oak bark by extraction alcohols may be used, for example, methanol, thereof with water, often under high pressure p opa o iSODYODaIIOI, butahols, and S0 Q and temperature, followed by filtration of the In general, a large excess, of aqueous alcohol is extract, then evaporation to obtain the solid used to extract the impurities from the Source This material is often referred to in material, 1. e., about 8 to about 50 ml. of aqueous Although we alcohol per gram of source material, depending prefer to use the powdered bark extract of comon the type of source material and its content merce it is obvious we can use the black oak bark of quercitrin. itself or any other product thereof which conduct d at r temperature to d as l ss of quercitrin in the liquid phase. Methods are known for isolating quercitrin carrying out this extraction, it is preferred to from black oak bark products but these known first treat the source material with a concenmethods give low yields and/or involve cumbertrated alcohol, about 85% to 100%, for example, One known method (Morrow 4c and. then after thorough mixing is obtained as and Sandstrom, Biochemical Laboratory Methy agitation r Standing, a measured amount ods, 2nd ed., 1935, pp. 231-2) involves the extracof water is added to bring the alcohol concentration of the solid bark extract with boiling water, tion to the proper level as heretofore defined. purification of the aqueous extract with activated It has been observed that by proceeding in this carbon, and crystallization of thequercitrin from fashion, a more efficient extraction of impurities the aqueous solution by cooling. This technique s Obtained. It i O v that the aqueous is cumbersome as it requires handling of alcohol extracts may be subjected to distillation enormous volumes of water as the quercitrin is or other treatments to recover the alcohol. soluble in water only to a limited extent. The second step of the process involves e2;- Another known method (Beilstein, Handbuch der tracting the solid material remaining from the ed., vol. XXXI, first extraction with acetone. pp. 75-6) involves extracting the bark product the quercitrin goes into solution whereas the alcohol, treatment of the impurities remain undissolved. alcoholic extract with lead acetate to precipitate tion of acetone with respect to water may be the impurities, removal of lead from the filtrate from about to 89% being preferred.

In this extraction it is preferred to have the acetone as hot as is possible without boiling away the acetone (about 50 C. is suitable) whereby the amount of solvent can be reduced to a minimum. The aqueous acetone extract so obtained is filtered while hot and the quercitrin recovered from the clear solution. This recovery may be obtained in several ways the preferred method involving adding an excess of water (say, about 1 to 4 volumes) thereto and then heating to evaporate off the acetone. During the evaporation the acetone vapors may be passed through a condenser to recover this solvent. The quercitrin which then precipitates out of solution is separated by filtration and dried.

If quercetin is the final product desired, then the quercitrin need not be isolated from the acetone extract. Instead, the acetone extract is treated with an acid to cause a hydrolysis whereby the quercitrin is converted into quercetin. An effective method for carrying out this hydrolysis involves adding 1 to 5% of concentrated sulphuric acid to the acetone extract, refluxing the reaction mixture for several hours to complete the hydrolysis and then separating the quercetin so formed. By proceeding in this manner, a substantially quantitative yield of pure, crystalline quercetin is obtained.

The following examples demonstrate particular conditions, steps, and materials within the scope of this invention. It is, of course, understood that these examples are merely illustrative and are not to be construed as a limitation of the invention to the particular details set forth.

EXAMPLE I (a) Extraction of impurities from bark extract Two hundred grams of powdered black oak bark extract was stirred vigorously into 330 ml. of 95% ethanol and then 5600 ml. of water was added to reduce the alcohol concentration to about 5%. The mixture was thoroughly agitated then allowed to stand for 24 hours. At the end of this time, the mixture was filtered on a vacuum filter to remove as much of the aqueous phase as possible.

(b) Extraction of qaercitrin The insoluble material from step a (crude quercitrin) was mixed with 600 ml. of anhydrous acetone. Due to the water content of the insoluble material, the concentration of acetone with respect to water was 81%. The mixture was heated to boiling and filtered while hot. The filtrate was poured into 3 liters of water and the acetone removed by heating the solution "on a steam bath. The quercitrin which crystallized out was removed by filtration and dried in an oven at 110 C. A yield of '78 grams of crystalline quercitrin was obtained.

EXAMPLE II (a) Extraction of impurities from bark extract Two hundred grams of powdered black oak bark extract was stirred vigorously into 665 ml. of 95% ethanol and the suspension allowed to stand for 12 hours. Then, 1135 ml. of water was added and thoroughly mixed with the suspension thus making the alcohol concentration 35%. The suspension was then allowed to stand for 24 to 48 hours. At the end of this time, it was noted that a layer of greyish-yellow solid material had deposited at the bottom of the vessel.

This material was recovered by decanting oiT the supernatant liquid.

(b) Extraction of qaercitrin The solid material from step a (crude quercitrin) was mixed with 750 ml. of hot (about 50 C). acetone. The liquid was filtered while hot to remove undissolved impurities. The clear, dark-red filtrate containing the quercitrin was then poured into 3 liters of water and the acetone removed from the solution by heating on a steam bath. The quercitrin which crystallized out was removed by filtration and dried in an oven at 110 C. A yield of approximately 80 grams of the crystalline quercitrin was obtained. This yield represents substantially all the quercitrin originally present in the starting material.

EXAMPLE III (a) Extraction of impurities from bark extract Two hundred grams of powdered black oak bark extract was stirred vigorously into 330 ml. of ethanol and then 5600 ml. of water was added to reduce the alcohol concentration to approximately 5%. The mixture was thoroughly agitated then allowed to stand for 24 hours. At the end of this time, the mixture was filtered using a vacuum filter.

(b) Ertraction of qaercitrin The insoluble material from step a (crude quercitrin) was mixed with 600 m1. of anhydrous acetone. Because of the moisture present in the insoluble material, the concentration or" acetone with respect to water was actually 81%. The mixture was heated to boiling and filtered while hot.

(0) Preparation of qaercetin The filtrate from step 2) (aqueous acetone solution of quercetin) was poured into 3 liters of water containing 40 ml. of concentrated sul phuric acid. The mixture was heated on a steam bath for 4 hours then filtered while hot. The crystalline quercetin collected on the filter was washed with water and dried in an oven at C. A yield of 50 grams of crystalline quercetin was obtained.

Having thus described our invention, we claim:

1. A process of isolating quercitrin from source materials containing the same, comprising extracting the source material, at about room temperature, with an aqueous lower alkanol having a concentration from about 5% to about 50%, by volume, of alkanol, separating the undissolved material, and extracting it with hot acetone to obtain an acetone extract containing quercitrin.

The process of claim 1 wherein the alkanol is ethanol.

3. The process of claim 1 wherein the source material is the solid extract of black oak bark.

4. A process of isolating quercitrin from the solid extract of black oak bark, comprising mixing, at about room temperature, the solid extract of black oak bark with an aqueous lower alkanol of about 95% concentration, by volume, of alkanol, mixing sufficient water with the resulting mixture to bring the alkanol concentration to about 5%, by volume, while maintaining the mixture at about room temperature, separatin the undissolved material, extracting it with hot acetone to obtain an acetone extract containing quercitrin, separating the acetone extract and acetone extract to acid hydrolysi to produce quercetin, and isolating the quercetin so pro duced.

FLOYD DE EDS. ALBERT N. BOOTH.

REFERENCES CITED The following references are of record in the file of this patent:

Wester Rec. Trav. Chim. 40 (1921), pp. 708- 710, 3 pages. 

1. A PROCESS OF ISOLATING QUERCITRIN FROM SOURCE MATERIALS CONTAINING THE SAME, COMPRISING EXTRACTING THE SOURCE MATERIAL, AT ABOUT ROOM TEMPERATURE, WITH AN AQUEOUS LOWER ALKANOL HAVING A CONCENTRATION FROM ABOUT 5% TO ABOUT 50%, BY VOLUME, OF ALKANOL, SEPARATING THE UNDISSOLVED MATERIAL, AND EXTRACTING IT WITH HOT ACETONE TO OBTAIN AN ACETONE EXTRACT CONTAINING QUERCITRIN. 